All negations don’t sound right to me.

I’m accustomed to hearing people make grammatical mistakes, but occassionally I’ll start hearing new and painful trends that are so pervasive that I wonder if someone changed the rules while I was asleep. Case in point: how to negate constructions containing the words “all” or “some”.
A few months ago, I was looking at some magazines at the grocery store and saw an ad asserting that “all insurance policies are not the same”. I’ve been hearing that kind of construction from high school kids for some time, but always attributed it to poor language skills. A few minutes later, I went to use the store’s bathroom and saw the following sign on the door: “All unpaid merchandise not allowed in restrooms”.
Now those of you who grew up in the America that I grew up in know that prior to the George H.W. Bush administration, such locutions would have read “Not all insurance policies are the same” and “No unpaid merchandise allowed in restrooms”. What has happened here? I now hear this “all...not” construction constantly and I’m not sure what to make of it. When I hear a teacher lament, “All of my 8th-graders didn’t finish their chapter test on time.”, what does she mean to communicate by that? Does she mean to say that NOT ONE of them finished (supported by literal deconstruction)...or that some did and some didn’t (supported by a higher likelihood of being the case)?

>Sorry UIP, but you're quite wrong. In formal logic, >"all X are not Y" does not in fact mean "no X are Y" >-- rather, it means "not all X are Y.

Sorry, amazed, simply asserting something does not make it so. More precisely, the universal quantifier, which is usually expressed as &ldquo;all&rdquo;, when preceding a statement about a variable, means that that statement is true for all values that that variable can take. I am confounded as to how you could possibly think that it means "not all X are Y&rdquo;. In what Math class did you learn that?

>If the "double negative" is wrong in English grammar on >the basis of "logic," should it not be wrong in French as well? >And yet, in French, the "double negative" is the standard >and it's colloquial to use a "single negative."

French doesn&rsquo;t have a double negative, it has a negative concord. English also has a negative concord. Note the difference between &ldquo;I saw something&rdquo; and &ldquo;I didn&rsquo;t see anything&rdquo;. The negation is marked in two places: the contracted &ldquo;not&rdquo;, and the switch from &ldquo;something&rdquo; to &ldquo;anything&rdquo;. Even though the negative is marked in two different places in the sentence, it&rsquo;s not a double negative. In French, if someone says &ldquo;Je ne parl pas&rdquo;, that means &ldquo;I don&rsquo;t speak at all&rdquo;. It does NOT mean &ldquo;I don&rsquo;t speak nothing&rdquo;. Implicit in your argument is that there has to be an exact one-to-one correspondence between words in different languages: for every word in one language, there has to be one, and exactly one, word that means exactly the same thing in the other language. This is ridiculous.

>And anyway, what is "logical" or not at the level of individual> grammatical usage is a highly subjective question.

2. Logic is universal so the laws of logic should apply equally in any language. If the "double negative" is wrong in English grammar on the basis of "logic," should it not be wrong in French as well? And yet, in French, the "double negative" is the standard and it's colloquial to use a "single negative." This is the complete reverse of English usage.

* And anyway, what is "logical" or not at the level of individual grammatical usage is a highly subjective question.

A few of you seem to forget that mathematics, specifically, logic and set theory, has an orderly and consistent set of formal rules that apply, well, to mathematics. Language is not mathematics. The structure "all x is not y" simply does not necessarily have the same formal and consistent definition in language as it does in mathematics.

Also, might it not also be possible that "All insurance policies are not the same" in an advertisement is exactly what the advertisers want to say? I would suggest that it's at least possible that they really don't mean "Not all insurance policies are the same" I think they mean exactly that every single insurance policy is different from every other insurance policy. That's part of the message. That's the only way they can claim that theirs is better than every other one. They need you to accept that no other policy can offer what theirs does.

"All that glitter is not gold" is from Shakespeare, so blaming Bush is rather uncalled for.

"Logically the sentence can have two meanings (I am sure someone more skilled than me in set theory can show this),"

In formal logic, "All X are not Y" ALWAYS means "no X are Y", because "not" always modifies whatever it's next to. It is only because people accept the idea that "not" can modify something else that the phrase is interpreted differently.

FlapJack, you are wrong. "All X are not Y" is not "very clear". The fact that everyone normally would interpret "All cars are not Ferraris" as "Not all cars are Ferraris", should be enough proof of that. How can you call it very clear when everyone normally interprets it the way you say is wrong? Logically the sentence can have two meanings (I am sure someone more skilled than me in set theory can show this), and since one of them (Not all X) is far more used than the other, that one should be used and not the other, to avoid confusion.

As an advertising professional, I see this construction all the time (as your example of the ad copy suggests), and I share your bewilderment. For what it's worth, as it was explained to me when I challenged my copywriters, the first construction "All insurance policies are not the same" takes some liberty to stress the "not" in the sentence. You might (or might not) agree that "Not all insurance policies are the same" seems a bit weaker--especially if you're the one selling them--than "All insurance policies are not the same." Almost by its awkwardness in the middle of the sentence, the "not" calls attention to itself, thereby doing its job as "good ad copy."

As for the second construction, that's just a result of a nitiwtted store manager who flunked 8th grade English. Nowhere have I encountered such grammatical mistakes as in retail shops. Fascinating.

In fact, the construction "All X are not Y" is very clear: it means that not one single X is Y. The action is negated for all the subjects.

Just because too many confuse "All X are not Y" and "Not all X are Y" (which negates some - not all - of the of subjects) doesn't mean the construction is unclear. It simply means that people do pay attention to the precision of the syntax.